Spring-flowering bulbs like daffodil (Narcissus sp.), hyacinth (Hyacinthus sp.), and crocus (Crocus sp.) are some of the earliest flowers to appear in gardens each year and are widely planted throughout the world (Armitage, 2008). Many species will bloom for years with minimal care, while others are best planted for one or two seasons of color. Spring bulbs will typically flower from late winter to early summer, depending on species (Dana et al., 2001). After bloom is finished, they continue to photosynthesize and store energy for a period before becoming dormant through summer and into fall (Chrungoo et al., 1983).
All spring bulb species have specific ecological niches that they prefer (Bryan, 2002), but many are found naturally in meadow areas that contain a combination of grasses, other monocots, and dicotyledonous plants. Some species such as crocus and snowdrop are still commonly found naturalized in meadows and mixed species environments (Bryan, 2002; Leeds, 2000). Although images of mixed bulb/grass lawns or meadows can be found in texts and on the Internet, a comprehensive literature search did not reveal any studies that examined these combinations in an experimental setting. In addition, most of the examples that could be found were from regions where cool-season grasses such as fescue (Festuca sp.), bentgrass (Agrostis sp.), and bluegrass (Poa sp.) would predominate. There has been renewed interest in mixed-stand lawns that provide color during certain times of the year or potentially fix nitrogen from the atmosphere via the inclusion of species such as white clover (Trifolium repens), yarrow (Achillea millefolium), yellow bedstraw (Galium verum), veronica (Veronica chamaedrys), and english daisy (Bellis perennis) (Cook, 2007; McCurdy et al., 2013; Rumball, 1989). These efforts confirm the growing interest in using polystands in certain lawn situations to improve the aesthetics and stability of those lawns.
Throughout the transition zone (U.S. Department of Agriculture hardiness zone 6), warm-season turfgrasses such as bermudagrass and zoysiagrass are commonly used in a variety of turf situations, including lawns and landscapes (Burton, 1974; Peterson et al., 2014). Although these grasses are persistent and provide an excellent surface for lawns, they also experience an extended dormancy period from late fall to spring. In the more northern regions of adaptation, this dormancy period can last for up to 6 months, from mid-October through early April (Baldwin et al., 2009; Patton and Reicher, 2007). Since these grasses are predominantly dormant during the period of flowering and growth of early spring bulbs, it was hypothesized that spring bulbs could be incorporated into a dormant lawn so that a show of spring color could be experienced before active growth of the turfgrass was started. For this system to work effectively, it would be desirable for the normal activity of the bulbs to be unaffected by routine cultural practices applied to turfgrass systems during that time, especially as it relates to herbicide applications or mowing.
The overall objective of this study was to examine the flowering capacity and persistence of several early spring bulbs in a zoysiagrass lawn. Zoysiagrass was chosen for this study since it is a very competitive warm-season grass against other plants and weeds (Busey et al., 1982) and would be considered the most difficult environment for bulbs to persist. A second objective was to examine the effects of common preemergence herbicides and mowing practices on the performance of the bulbs.
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